Transmit beamforming relies on coherent transmission by spatially separated antennas forming constructive interference at the intended receiver. These spatially diverse antennas may be part of an array, multiple-input and multiple-output (MIMO) system or, separate wireless nodes. In the latter case, nodes during beamformed transmissions obtain the packet and a referenced time, common to all, to begin sending.
It is often assumed that nodes are within one-hop, or that a time division multiple access (TDMA)-based MAC schedules the beamformed transmission immediately after dissemination. Reliance on TDMA MAC with scheduling of long link transmission in same round as packet dissemination means scheduling is not used for State-of-the-art data dissemination and scheduling on the beamformed link relies on TDMA-based solutions in which a common schedule is established to deliver copies of the original single-sourced packet to beamforming nodes. Packets are sent on the beamformed link immediately after in-network dissemination, thus obviating the need for scheduling. Perfect communications and one-hop networks are generally assumed. Works that have considered multiple-hop networks use a clustering solution to reduce the problem to that of one-hop networks.
However, if more than one hop is involved, dissemination means nodes receive a copy of a packet at different times. The network cannot wait for nodes to receive one packet and then transmit on the uplink within the same round. Further, the uplink pipe is to be kept full. Packets are to be sent out on uplink at same time by nodes participating in distributed beamforming and dissemination failure is not a cause of conflict/interference.